The present invention relates generally to the valve train of an internal combustion engine and, more particularly, to a springless poppet valve system.
Conventional poppet valve systems used in four-stroke internal combustion engines are typically biased to a closed position using a spring. The valve is moved to an open position against the force of the spring by a cam or cam-actuated rocker arm. On the open stroke of the valve, the cam or rocker arm also must move the valve counter to the momentum of the valve such that the open force required is effectively doubled. These conventional poppet valve systems, however, are limited with regard to speed at which the valves can be actuated. As will be appreciated, the limit on the valve actuation speed, in turn, limits the rate at which the engine can turn (i.e., engine rpm). As engine torque and speed dictate engine power, limits on the engine rpm constrain the power of an engine.
In particular, increasing the actuation speed of the valve necessarily increases the force and stress applied to the components of the valve train. To compensate for the increased force and stress, the valve train components must be made stronger. Strengthening the valve train components is most often achieved by increasing the mass of the components. This increased mass, however, requires the use of a stiffer valve spring which, in turn, further increases the force and stress on the valve train components. Moreover, increasing the mass of the valve train components increases the overall weight of the engine and, therefore, has a detrimental effect on engine performance. Thus, a balance between the stiffness of the valve spring and the mass of the. valve train components limits the peak valve actuation speed of a valve train.
Removing the spring from the valve train alleviates the issues regarding the force need to open the valve, however, such springless valve systems are expensive to manufacture and maintain. Specifically, current springless valve systems must be manufactured and assembled to very tight tolerances in order to prevent lash or binding in the system. Additionally, during operation, because of the tight tolerances that are required, springless poppet valve systems frequently have to be adjusted resulting increased maintenance requirements.
Accordingly, in view of the foregoing, a general object of the present invention is to provide a poppet valve system for an internal combustion engine which overcomes the problems associated with existing poppet valve systems.
A more specific object of the present invention is to provide a poppet valve system as characterized above which can achieve higher valve actuation speeds than existing springless poppet valve systems.
Another object of the present invention is to provide a poppet valve system as characterized above which is less costly to manufacture and assemble than existing springless poppet valve systems.
A further object of the present invention is to provide a poppet valve system as characterized above which requires less maintenance than existing poppet valve systems.